BACKGROUND OF THE INVENTION
[0001] This invention concerns a transistor circuit. In particular, it concerns a transistor
circuit which provides a constant-current source circuit which can operate with a
low power source voltage threshold and is minimally dependent on its electric power
source, and a constant-voltage circuit which makes use of these properties of the
constant-current circuit.
[0002] In-recent years, with the miniaturization of portable audio equipment, cameras, etc.,
the demand has increased for constant-current and constant-voltage circuits which
are unaffected, even at low voltages, by variations in power source voltage, temperature,
etc.
[0003] Various type of constant-current and constant-voltage circuits have been proposed
before. The present invention aims to meet the demand referred to above by improving
on such circuits. An explanation is given first of the prior art.
[0004] Fig. 1(A) is a constant-current source which makes use of a current mirror circuit.
The two emitters, and the two bases, of the two NPN type transistors 1 and 2 are respectively
connected in common. The emitters are connected to the first power supply terminal
G. The collector and base of the transistor 1 are connected together, and via the
resistor 3 are connected to the second power supply terminal V
CC. Since the voltage V
BE between the base and emitter of each of the transistors 1 and 2 is the same, the
collector currents of the two transistors will be equal if their structural dimensions
are the same; and consequently the output current I
out can be expressed as follows
where
R is the resistance of the resistor 3 and V
CC the voltage at terminal V
CC.
[0005] Since however the output current I
out depends on the voltage V
CC of the power supply, the properties of the circuit are less than satisfactory, as
is shown by Fig. 1(B).
[0006] Fig. 2 shows examples of conventional circuits which have been improved by reducing
the effect of the power supply on the current values. If the structural dimensions
of the transis- tors 21, 22 and 23, and 26 and 27 in the layout of the circuits shown
in Figs. 2(A) and (B) are all made equal, a voltage equal to the voltage V
BE between the base and emitter of the transis- tors will be produced at the resistors
24 and 28 shown in the circuits. Consequently, if the base-common-current amplification
factor α of each of the transistors 22 and 27 is taken as being 1, the output current
I
out is expressed in each case by
where R is the resistance of the resistors 24 and 28.
[0007] As formula (2) shows, in a current source circuit of this type the output current
I
out does not depend on the voltage V
CC of the power supply. However, such circuits will not operate unless the base potential
of the respective transistors 22 or 27 is at least twice the voltage V
BE between base and emitter. Their operating properties are shown in Fig. 2(c), and
there is no output current I
out until V
CC exceeds 1.4V.
[0008] Fig. 2(D) is an example of a current mode logic (CML) circuit using the circuit illustrated
in Fig. 2(A) as its current source. The common emitters of the two transistors 30-1
and 30-2 are connected to the collector of the transistor 22; the collector of each
of the transistors 30-1 and 30-2 is connected, via the resistors 30-3 and 30-4, to
the power supply terminal V
CC. One of the transistors 30-1 and 30-2 turns ON as a result of the relationship between
the electric potentials of the inputs applied to the respective bases of the two transistors;
and the output is obtained via the resistor 30-3 or the resistor 30-4. This circuit
will not operate unless at least the electric potential of the collector of the transistor
21 is more than 2V
BE, ie. at least approximately 1.4V; and this means that the electric potential of the
collector of the transistor 22 must also be at least 1.4V. Further, for the logic
circuit to respond to the inputs applied to the bases of the transistors 30-1 and
30-2, a voltage applied to these bases must be at least V
BE (ie. 0.7V) added to 1.4V.
[0009] Thus a voltage of at least 2.1V must be applied to the collectors of transistors
30-1 and 30-2. Therefore the power supply voltage must be at least 2.1V.
[0010] Fig. 3 shows a conventional circuit which has been improved to reduce the threshold
voltage of a constant-current source circuit. The transistor 31 is biased by the series
circuit of resistors 33 and 34 connected between the base of the transis- for 32 and
the power supply terminal G. We can assume that the relation between the resistances
R
33 and R
34 of the resistors 33 and 34 is'set at
Then, if the voltage drop across R
33 is greater than the base-emitter voltage V
BE of the transistor, ie. at least approximately 0.7V, the transistor 31 will be in
a conducting state. Since the base-emitter voltage V
BE of the transistor 31 is kept constant at approximately 0.7V even though the power
supply voltage V
CC may be larger the base potential of the transistor 32 is also kept constant at (1+k)
V
BE.
[0011] Consequently, since the voltage drop occurring across the resistor 35 connected between
the emitter of the transistor 32 and the power supply terminal G is k V
BE, the collector current of the transistor 32, or in other words the output current
I
out, can be expressed as follows
where R
35 is the resistance of the resistor 35. But this type of circuit will not operate unless
the power supply voltage V
CC is more than (1+k)V
BE, as shown in Fig. 3(B).
SUMMARY OF THE INVENTION
[0012] Accordingly, an object of the present invention to provide a transistor circuit which
will operate at a low voltage, and which will supply constant current or constant
voltage which does not depend on the voltage of the power source.
[0013] To achieve the above object, a transistor circuit has a first terminal responsive
to a power supply voltage, and a second terminal connected to a reference voltage.
First and second cir- cuit portions are connected in parallel between these terminals.
The first and second circuit portions are responsive to the supply voltage to cause
respective first and second currents, which are proportional to the power supply voltage,
when the power supply voltage exceeds first and second predetermined voltage levels
respectively.
[0014] Circuit means is connected to the first and second circuit portions for producing
a differential current of the first and second currents. The differential current
is a constant-current. A constant-voltage can be obtained by using the constant-current.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Other objects and advantages of the invention will be apparent from the following
description taken in connection with the accompanying drawings, in which:
Fig. 1(A) is a circuit diagram of a conventional current source, and Fig. 1(B) is
the voltage-current characteristic thereof.
Figs. 2(A) and (B) are circuit diagrams of other conventional current sources, and
Fig. 2(C) is the voltage-current characteristic for them.
Fig. 2(D) is a circuit diagram of a CML circuit using the circuit illustrated in Fig.
2(A) as its current source.
Fig. 3(A) is a circuit diagram of another conventional current source, and Fig. 3(B)
is the voltage-current characteristic thereof.
Fig. 4(A) is a circuit diagram of a first preferred embodiment of a transistor circuit
according to the present invention.
Fig. 4(B) is a circuit diagram of a second preferred embodiment of a transistor circuit
according to the present invention and Fig. 4(C) shows the voltage-currrent characteristic
of the transistor circuits illustrated in Figs. 4(A) and (B).
Figs. 4(D) and (E) are circuit diagrams of additional third and fourth embodiments
of transistor circuits according to the present invention.
Figs. 5(A) and (B) show applications of the transistor circuit according to the present
invention to CML circuits.
Fig. 6 is a circuit diagram of a further, fifth embodiment according to the present
invention.
Fig. 7(A) is a circuit diagram of a sixth embodiment according to the present invention,
arid Fig. 7(B) shows the voltage- current characteristics thereof.
Fig. 8(A) is a circuit diagram of a seventh embodiment of a transistor circuit according
to the present invention, and
Fig. 8(B) shows an application of the transistor circuit illus- trated in Fig. 8(A).
Fig. 9 shows an application of the transistor circuit illustrated in Figs. 4(B) and
8(A).
Fig. 10 is a circuit diagram of an eighth embodiment according to the present invention.
Fig. 11 is a circuit diagram of a ninth embodiment according to the present invention.
Fig. 12 is a circuit diagram of a tenth embodiment according to the present invention.
Fig. 13 shows an operation characteristic of the transistor circuit illustrated in
Fig. 12.
Fig. 14 is a circuit diagram of the eleventh embodiment according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] Some preferred embodiments of the invention are explained below with reference to
the drawings.
[0017] Fig. 4(A) is a circuit diagram showing the basic layout of - the transistor circuit
of this invention.
[0018] In a first circuit portion 40-1 a current flows which is a function of the power
supply voltage V
CC when the latter is greater than a first voltage V
1.
[0019] Circuit portion 40-1 is a series circuit consisting of the resistor 45 and the diodes
42 and 43, connected between the power supply terminal V
CC and ground terminal G. The current I
1 flowing through this first circuit can therefore be expressed as
where V
F is the forward direction voltage of the diodes, and R
45 is the resistance of the resistor 45.
[0020] In a second circuit portion 40-2 a current flows which is a function of the power
supply voltage V
CC when the jatter is greater than a second voltage V
2. Circuit portion 40-2 consists of the resistor 46 and the diode 44 connected in series
between the first power supply terminal V
CC and the second power supply terminal G. The current I
2 through resistor 46 in the second circuit portion can be expressed as
where V
F is the forward direction voltage of the diode 44, and R
46 is the resistance of the resistor 46.
[0021] Transistor 41 performs the function of subtracting the currents one from the other,
flowing in the two circuits already described. That is to say, the current I
1 flowing in the first circuit part is substracted from the current I
2 flowing through the resistor 46. The base of transistor 41 is connected to the junction
of the diodes 42 and 43, its emitter to terminal G, and its collector to the junction
of the resistor 46 and the
diode 44. Thus, since the diode 42 and the transistor 41 form a current mirror circuit,
if the base common current amplification factor of the transistor 41 is taken as 1,
its collector current I
C is then equal to I
1. Consequently, the current I through the diode 44 is
with the following result, that if
R45 = R46 = R,
[0022] Fig. 4(B) shows the case where diode connected transistors have been substituted
for the diodes in the circuit of Fig. 4(A), a current mirror circuit is formed by
the diode-connected transistor 44 (corresponding to the diode 44) and the transistor
44-1, and output current I
out is obtained from transistor 44-1.
[0023] In this circuit, I
out is equal to the collector current of transistor 44, ie. to the current I through
the diode 44 in Fig- 4(A). The voltage-current properties of this circuit are as shown
in Fig. 4(C).
[0024] When the power supply voltage V
CC is more than the second voltage V
2 (V or V
BE, the voltage between the base and emitter BE of the transistor), the output current
I
out is a function of the power supply voltage - that is the current is expressed in formula
(6). When the voltage exceeds the first voltage V
1 (2V
F or 2V
BE), the output current is supplied as the constant-current expressed by formula (8).
'This is shown in Fig. (c).
[0025] In the circuit of Fig. 4(D) the value of the output current I
out is smaller than that of the current through the transistor 44 because of the resistor
47 connected between the emitter of the transistor 44-1 and the power terminal G.
[0026] In Fig. 4(E), conversely, the intention is to obtain an output current I
out larger than I. The transistors 44-1
44-n are provided to form n current mirror circuits with the transistor 44; the bases,
emitters and collectors of these transistors 44-1
44-n are respectively commonly connected together, and lout is obtained from the
common collector terminal.
[0027] Consequently, if the structural dimensions of the transis- tor 44 and the transistors
44-1
44-n are made identical, a cur- rent of n times the current through the transistor
44 is obtained as I
out.
[0028] Fig. 5(A) shows an example of a circuit in which the tran- sistor circuit of this
invention is applied to the current source of a CML circuit. Using the current source
circuit shown in Fig. 4(B), the commonly connected emitters of the transistors 40-1
and 40-2 are connected to the collection of transis- tor 44-1. In this circuit, as
previously explained, the electric potential of the collector of transistor 44 must
be greater than V
BE of the transistor, ie. more than 0.7V for current to be available at the collector
of the transistor 44-1. Consequently, for the C
ML circuit to function, it is sufficient if an input voltage of approximately 1.4V
is impressed on the bases of the transistors 40-1 and 40-2, and if a similar voltage
is applied to the collectors. Compared with the requirement for a supply volt- : age
of at least 2.1V in the conventional circuit of Fig. 2(D), therefore, this circuit
can operate at a much lower voltage.
[0029] Fig. 5(B) shows an embodiment involving a CML layout in several (n) stages. The resistor
47 connected at the nth stage between the transistor 44-n and the terminal G is for
current setting.
[0030] Fig. 6 is a circuit diagram of another embodiment of the invention. The base and
collector of transistor 42 are connected together via the base-emitter junction of
transistor 43. The aim here, in contrast to an embodiment such as that illustrated
in Fig. 4(B), where the base and collector of the transistor 42 are directly connected,
is that the current flowing from the collector of the transistor 42 to the junction
of the bases of the transistors 41 and 42 should be multiplied by (1-α), and that
the collector currents of these two transistors should be matched more closely. In
this embodiment, a constant-current is obtained from the collector of the transistor
44-1 when the electric potential of the base of the transistor 43' is at least 2V
BE.
[0031] Figure 7(A) is a circuit diagram showing another embodiment of the invention. It
shows an example of a circuit in which the threshold value of the power supply voltage
for the supply of a constant-current is (1+k)V
BE. The bases of the transistors 41 and 42 are connected in common and are biased by
resistors 47 and 48 connected in series between the collector of the transistor 42
and the power supply terminal G. Therefore when the voltage drop across the resistor
47 is greater than V
BE of the transistor, the transistor is placed in a conducting state. If the resistances
of the resistors 47 and 48 at this point are taken as R
48 = k.R
47 (where R
47 and R
48 are the resistances of the resistors 47 and 48 respectively, and k is an arbitrary
constant), the electric potential of the collector of transistor 42 is (1+k)V
BE. The current I
1 flowing through the resistor 45 is therefore as fol- lows.
[0032] Further, when the electric potential on the collector of transistor 44 is greater
than V
BE, the current I
2 flowing through the resistor 42 has a value which is a function of the power sup-
pl
y voltage V
CC, and can be expressed as follows.
where R45 and R
46 are the resistances of the resistors 45 and 46.)
[0033] Consequently, the collector current of transistor 44, and therefore the output current
I
out, is as follows.
Here, if R
45 = R
46 = R, formula (11) can be expressed-as follow.
[0034] Consequently, the relation between the output current I
out and the power source voltage V
CC is as shown in Fig. T(B). When the power supply voltage V
cc is more than V
BE of the transistor (approximately 0.7V), an output current I
out which is a function of the power supply voltage begins to flow; when V
CC exceeds (1 + k)V
BE, I
out becomes constant and is expressed as kV
BE/R.
[0035] Fig. 8(A) is a circuit diagram showing an embodiment in which the constant current
obtained by the transistor circuit of this invention is used as an injection current
in I
2 circuits. In the diagram, nI
2L circuit stages from.95-1 to 95-n are connected between the collector of the transistor
41 and the power supply terminal G. Each I
2L circuit consists of an injection transistor 95-11 ~ 95-nl and an output transistor
95-21 ~ 95-2n: inputs I
n-1 ~ I
n-n are applied at the bases of the output transistor 95-21 ~ 95-2n.
[0036] In this circuit layout, a virtual diode 44, derived from the base - emitter junctions
of the injection transistors of the I
2L circuits is connected between the collector and emitter of the transistor 41.
[0037] -Consequently, the operation of the circuit as a constant-current source circuit
is similar to what occurs in the basic circuit layout explained above with reference
to Fig. 4(A). The only difference is that when nI
2L circuits are connected, the injection current I
inj for each I
2L circuit is as follows.
[0038] When the transistor circuit of this invention is used in this way, the power source
threshold is a low voltage (approxi--mately 0.7V), and a constant injection current
is obtained when the power supply voltage is equal to 2V BE (approximately 1.4V) or
higher.
[0039] Fig. 8(B) is a circuit diagram of an embodiment applied to a 4 bit D/A converter
made up of I
2L circuits using the present invention source. I
n-1 is the least significant bit (LSB) input, and I
n-4 the most significant bit (MSB) input. The input I
n-1 is the input to a stage consisting of a single I
2L circuit G
1-1,
[0040] I
n-2 to a stage consisting of two I
2L circuits G
2-1 ~ G
2-2, I
n-3 to a stage consisting of four I
2 circuits G
3-1 ~ G
3-4, and In
n-4 to a stage consisting of eight I
2L circuits G
4-1 ~ G
4-8. The outputs of the respective I
2L circuits are.connected in common to the output terminals Out
1, Out
2, Out
3, and Out
4. These output terminals are further connected in common via a load resistor 49 to
the power supply terminal V
CC. In this circuit layout, when any input is at the logic level '1', the output transistor
(or transistors) of the corresponding I
2L circuit stage turns ON, and output current is obtained weighted by the number of
I
2L circuits turned ON, in response to the respective inputs. The voltage drop across
the resistor 49 developed by the sum of these output currents is obtained as an analog
output.
[0041] In this circuit layout too the device becomes operational at a low voltage (approximately
0.7V), and at and above 1.4V a constant injection current is supplied to each I
2L circuit. The injection current I
inj for each I
2L circuit under constant- current operation is indicated in this case by
where R is the resistance of the resistors 45 and 46.
[0042] Fig. 9 is a circuit diagram of an embodiment which combines the layouts of Figs.
5 and 8. In this circuit too a CML circuit is provided which will operate at a low
voltage. A first transistor circuit of this invention is used as the means of supply-
ing injection current for the I
2L circuits, and a second transistor circuit (identified by the same numbers with prime)
as the current source for the CML circuit. Further description of the operation of
this circuit is not required since it cperates as described above for the similar
corresponding circuits.
[0043] Fig. 10 is a circuit diagram of another embodiment of the invention, designed to
obtain a micro-current. The difference in layout from the embodiment of Fig. 4(B)
is the circuit connected between the collector of the transistor 41 and the power
supply G.
[0044] This circuit consists of two transistors 11 and 12, with their respective emitters
connected to the power supply terminal G. The base of the transistor 11 is connected
to the collector of the transistor 41, and the resistor 13 is connected between the
base and the collector of the transistor 11. The base of transistor 12 is connected
to the collector of transistor 11, and the collector of the transistor 12 constitutes
the output terminal of the circuit.
[0045] The output current I
out in this diagram is found in the fol- lowing manner. If V
BE11 and V
BE12 are the respective voltages between the base and emitter of the transistors 11 and
12, while
R is the resistance of the resistor 13, and I the current through it, the following
formula results.
Further, the current I
1 through the resistor 45 is found as follows:
where V
BE42 and V
BE43 are the voltages between base and emitter of the transistors 42 and 43, and R
45 is the resistance of the resistor 45.
[0046] Further, the current I
2 flowing through the resistor 46 is expressed as follows:
where
R46 is the resistance of the resistor 46, and V
BE11 the voltage between base and emitter of transistor 11.
[0047] Consequently, since the current
I consists of the current which is the difference between I
1 and I
2,
where R
45 = R
46 = R, and V
BE11 =V
BE42 = V
BE43 = V
BE, which gives the following.
[0048] Further, the base-emitter voltages V
BE11 and V
BE12 of the transistors 11 and 12 are expressed as follows:
where q is the amount of electric charge of one electron, k is the Boltzmann constant,
T is the absolute temperature, and I
s is the saturation current.
[0049] If the base-emitter voltage V
BE12 of the transistor 12 is expressed in terms of the output current I
out, we have
which gives, from formulae (20) and (21),
leading, if this equation is solved, to
where V
T =
(thermovoltage).
[0050] Fig. 11 is a circuit diagram showing an application of the transistor circuit of
this invention to a constant-voltage source circuit. Transistor 14 is connected between
the collector of transistor 41 and the power supply terminal G, its emitter being
connected to the power supply terminal G and its collector to the collector of the
transistor 41. Further, a series circuit consisting of resistors 15 and 16 is connected
between the collector of transistor 14 and the power supply terminal G, the junction
between them being connected to the base of the transistor 14.
R15 and
R16 are now taken as the resistances of the resistors 15 and 16 respectively, and it
is postulated that R
15 = k R
16, where k is an arbitrary constant.
In this circuit of Fig. 11, collector current begins to flow in the transistor 14
when the voltage drop across the resistor 16 exceeds approximately 0.7V.
[0051] If the base-emitter voltage of the transistor 14 is taken as V
BEl4, the voltage between emitter and collector is expressed as (1 + k)V
BE14. Consequently, the current I flowing through the resistor 46 is expressed as follows:
Iwhile the current I
1 through the resistor 45, on the other hand, is expressed as follows:
where V
BE42 and V
BE43 refer to the transistors 42 and 43. Consequently, assuming that V
BE42 = V
BE43 = V
BE14 = V
BE, and that in the case of the resistances of the resistors 45 and 46, R
45 =
R46
= R, the collector current of the transistor 14, if the current flowing through the resistors
15 and 16 is ignored, is expressed by the following:
and a voltage (l + k) times the base-emitter voltage of the transistor 14, which is
determined by the current I expressed by this formula (28), is obtained from the V
out terminal connected to the collector of the transistor 41. The collector current of
the transistor 14 is made constant at the value indicated by formula (28). Because
V
BE is stable, V
out is stabilized at V
out = (1 + k)v
BE.
[0052] Fig. 12 is a circuit diagram showing another embodiment of the application of the
invention to a constant-voltage source circuit. The circuit illustrated in the diagram
is formed by providing the circuit shown in Fig. 11 with further transistors 17 and
18 and a further resistor 19. The collector of the transistor 17 is connected to the
power supply terminal V
CC, its base to the collector of the transistor 41, and its emitter to the output terminal
V
out. The collector of the transistor 18 is connected to the output terminal V
out; its base is connected in common to the base of the transistor 14, and its emitter
is connected via resistor 19 to the power supply terminal G.. The circuit portion
10 surrounded by the broken line is the subject of Japanese Patent application No.
54-80099 by the inventor of the present invention. If we postulate that
R = R
15/R
16 (R
15 and α R
16 being the resistance of the resistors 15 and 16), the supply of a constant current
I makes it possible to provide a constant voltage source with output voltage v out
atα
R time the energy gap voltage V
g0 of silicon at O*K and with a temperature coefficient of 0.
[0053] Fig. 13 is a graph showing the results of experiments with the circuit illustrated
in Fig. 12. It will be seen that when the power supply voltage exceeded 1.4V, a virtually
constant output voltage was supplied even when the temperature was varied.
[0054] Fig. 14 is a circuit diagram showing an embodiment consisting of another application
of the invention as a constant-voltage source. The bases of the transistors 41 and
42 are biased by means of a series circuit consisting of the resistors 47 and 48.
The effect is, as explained in connection with the embodiment illustrated in Fig.
7, to commence constant-voltage operation from a lower voltage. As explained above,
this invention makes it possible for operation to start at a low power supply voltage
(approximately 0.7V); and since it can be used as a low-voltage, constant-current
and constant-voltage source, the range of applications is extremely wide. Operation
can be achieved with a single 1.5V battery, for example, and this will greatly assist
the miniaturization devices such as portable audio devices.
1. A transistor circuit having first and second terminals driven by a power supply
voltage applied across the terminals comprising:
first and second circuit portions connected in parallel between said first and second
terminals, said first and second circuit portions responsive to said supply voltage
to cause respective first and second currents proportional to said power supply voltage
when said power supply voltage exceeds respective first and second predetermined voltage
levels, and
circuit means being connected to said first and second circuit portions for producing
a differential current of said first and second currents.
2. A transistor circuit according to claim 1, wherein said first circuit portion comprises
first resistor means having first and second ends, said first end being connected
to said first terminal, and first and second diode means connected between said second
end of said first resistor means and said second terminal;
said second circuit portion comprises;
second resistor means having first and second ends, said first end being connected
to said first terminal, and -third diode means connected between said second end of
said second resistor means and said second terminal; and said circuit means comprises;
first transistor means having an emitter electrode connected to-said second terminal,
a base electrode connected to a connection of said first and second diode means, and
a collector electrode connected between said second resistor means and said third
diode means.
3. A transistor circuit according to claim 2, wherein said first and second resistor
means having the same resistance.
4. A transistor circuit according to claim 2, wherein said third diode means is a diode-connected
transistor having an emitter electrode connected to said second terminal, a collector
electrode connected to said second end of said second resistor means, and a base electrode
connected to said collector electrode thereof.
5. A transistor circuit according to claim 4, which further comprises a second transistor
having an emitter electrode connected to said second terminal, a base electrode connected
to said base electrode of said diode-connected transistor, and a collector electrode
connected to an output terminal.
6. A transistor circuit according to claim 2, wherein said third diode means comprises
second and third transistor means, and said second transistor means has an emitter
electrode connected to said second end of said second resistor means, a base electrode
connected to said second terminal, and a collector electrode connected to an input-terminal,
and said third transis- for means has an emitter electrode connected to said second
terminal, a base electrode connected to said input terminal, and a collector electrode
connected to an output terminal.
7. A transistor circuit according to claim 1, wherein said first circuit portion comprises
first resistor means having first and second ends, said first end being connected
to said first terminal,
first transistor means having an emitter electrode, a base electrode connected to
said second end of said first resistor means and a collector electrode connected to
said first resistor means and a collector electrode connected to said second end of
said first resistor,
second transistor means having an emitter electrode connected to said second terminal,
a collector electrode connected to said emitter electrode of said first transistor
means, and a base electrode connected in common with said collector electrode,
said second circuit portion comprises second resistor means having a first and second
ends, said first end being connected to said first terminal,
diode means connected in series between said second end of said second resistor means
and said second terminal, and
said circuit means comprises third transistor means having an emitter electrode connected
to said second terminal, a base electrode connected to said base electrode of said
second transistor means, and a collector electrode connected to said second end of
said second resistor means.
8. A transistor circuit according to claim 7, which further comprises fourth transistor
means having an emitter electrode connected to said second terminal, a base electrode
connected to said second end of said second resistor means, and a collector electrode
connected to an output terminal.
9. A transistor circuit according to claim 1, wherein said first circuit portion comprises
first, second and third resistor means being connected in series between said first
and said second terminal,
first transistor means having an emitter electrode connected to said second terminal,
a base electrode connected between said second and third resistor means, and a collector
electrode connected between said first and second resistor means,
said second circuit portion comprises
fourth resistor means having first and second ends, said first end being connected
to said first terminal,
diode means connected in series between said second end of said fourth resistor means
and said second terminal; and
said circuit means comprises second transistor means having an emitter electrode connected
to said second terminal, a base electrode connected to said base electrode of said
first transistor means, and a collector electrode connected to said second end of
said fourth resistor means.
10. A transistor circuit Recording to claim 1, wherein said first circuit portion
comprises
first resistor means having first and second ends, said first end being connected
to said first terminal,
first and second diode means connected in series between said second end of said first
resistor means and said second terminal;
said second circuit portion comprises
second resistor means having first and second ends, said first end being connected
to said first terminal,
third resistor means having first and second ends, said first end being connected
to said second end of said second resistor means,
first transistor means having an emitter electrode connected to said second terminal,
a base electrode connected to said second end of said second resistor means, a collector
electrode connected to said second end of said third resistor means,
second transistor means having an emitter electrode connected to said second terminal,
a base electrode connected to said second end of said third resistor means, a collector
electrode connected to an output terminal.
11. A transistor circuit according to claim 1, wherein said first circuit portion
comprises
first resistor means having first and second ends, said first end being connected
to said first terminal,
first and second diode means connected in series between said second end of said first
resistor means and said second terminal,
said second circuit portion comprises
second, third and fourth resistor means connected in series between said first and
second terminals,
first transistor means having an emitter electrode connected to said second terminal,
a base electrode connected to a connection of said third and fourth resistor means,
and a collector electrode connected between said second and third resistor means,
and
said circuit means comprises second transistor means having an emitter electrode connected
to said second terminal, a base electrode connected between said first and second
diode means, and a collector electrode connected to said collector electrode of said
first transistor means.
13. A transistor circuit comprising;
a first terminal supplied with a power supply voltage,
a second terminal supplied with a reference voltage,
first biasing means connected between said first and second terminals, and which causes
a first current when said power supply voltage exceeds a first predetermined voltage
level,
second biasing means connected between said first and second terminals, and which
causes second current when said power supply voltage exceeds a second predetermined
voltage level lower than that.of said first predetermined voltage level,
first transistor means having an emitter electrode, a base electrode and a collector
electrode, and the base to emitter junction thereof is biased with said first biasing
means, and a collector to emitter junction thereof is biased with said second biasing
means, thereby producing a differential current of said first and second currents.
14. A transistor circuit according to claim 13, which further comprises;
second transistor means having an emitter electrode, a base electrode and a collector
electrode, and a base to emitter junction thereof is biased.with said second biasing
means, and
means for connecting said collector electrode tc an output terminal.